A Brachistochrone Curve Marble Racing Demonstrator

In 1696, Johann Bernoulli posed the question in the scientific journal Acta Eruditorum, of what is the quickest path is between two points…

In 1696, Johann Bernoulli posed the question in the scientific journal Acta Eruditorum of what is the quickest path is between two points at different elevations when a frictionless marble is traveling under a uniform gravitational pull. The solution, known as the brachistochrone curve — a sort of portmanteau of the ancient Greek brákhistos khrónos, or ‘shortest time’ — remains a classic physics problem to this day. In order to demonstrate how this works in real life, creator “Technovation Projects” has created a brilliant marble run setup.

The model implements three independent marble runs, each constructed from a pair of laser-cut acrylic sheets cut to a specific curve. Marbles are dropped simultaneously from a mechanical holder apparatus, and allowed to roll until each hits a microswitch at the bottom. An Arduino Uno-controlled timer assembly tells which one hit first, with user output provided via a 16x2 LCD screen.

The result, as seen in the video below, is an exciting demonstration that should be very interesting for physics students, even more so if they’re able to build it themselves. Every marble race would have predictable results, though further experiments could be done with releasing marbles at different points, or perhaps one could even tilt the rig to see how it affects things!